1. Field of the Invention
The present invention relates to an optical connector to be used in an automobile or the like, and more particularly to the optical connector of a male type which includes a ferrule for an optical fiber cable mounted inside an annular wall of a housing, and aims to enhance rigidity of the housing while protecting the annular wall.
2. Description of the Related Art
Heretofore, for connection of auxiliary equipments in the automobile, there has been employed a wire harness which is an assembly of electric wires. However, it has been a problem that the wire harness has recently grown bulky and heavy with an increase in number of the auxiliary equipments and circuits therefor. In order to solve this problem, means for transmitting signals to the auxiliary equipments by means of optical fiber cables are employed in a part of the wire harness.
FIG. 9 shows one example of a conventional optical connector.
An optical connector 35 is composed of a male type optical connector (optical plug) 21 and a female type optical connector (receptacle) 36. The male type optical connector 21 is inserted in an engaging chamber 37 of the female type optical connector 36, and locked by a lock arm 27. The female type optical connector 36 is fixed to a circuit board 39 by means of bolts 40 at fixation parts 38 on both sides.
As also shown in FIG. 10, the male type optical connector 21 has ferrules 41 connected to optical fiber cables 33 or having the optical fiber cables 33 passed therethrough, in a male type housing 26 made of synthetic resin. The ferrules 41 are supported by receiving parts 50 which are integral with the housing 26, and biased forward (in an engaging direction of the connector) by means of a helical spring 42 to move back and forth to an extent where an intermediate flange 43 comes in contact with the receiving parts 50 and locking projections 51. Distal ends of the ferrules 41 respectively project into engaging chambers 52 in the housing 26.
As also shown in FIG. 11, the female type connector 36 has a female type housing 44 made of electrically conductive synthetic resin, and receiving trunks 45 in a cylindrical shape for the above mentioned ferrules 41 are integrally formed inside the housing 44. The receiving trunks 45 integrally project from a vertical partition wall 13 which defines the engaging chamber 37 of the housing 44. The housing 44 is fixed in contact with an earth circuit (not shown) of the circuit board 39 by means of the fixation parts 38 (See FIG. 9) on both sides in its backward half and by means of positioning pins 46 or so in its forward half.
A sleeve 14 is inserted into a large diametered portion 45a of each of the receiving trunks 45 in its backward part. The sleeve 14 is composed of a wave guide passage (not shown) in the center formed of glass or synthetic resin and a cylindrical holder formed of metal. Inside the housing 44, light converting elements (photo electric elements) 12 are arranged behind and adjacent to the receiving trunks 45. The sleeves 14 are in contact with the light converting elements 12. The light converting elements 12 are connected to the circuit board 39 by means of lead terminals 19 and pressed from the back by a cover 47 toward the receiving trunks 45.
The light converting elements 12 include a light emitting element such as a light emitting diode and a light receiving element (photo detector) such as a photodiode which are arranged in parallel to each other correspondingly to the two optical fiber cables 33 of the male type optical connector 35.
In FIG. 9, when the male type optical connector 35 is inserted into the engaging chamber 37 of the female type optical connector 36, small diametered portions 41a at forward ends of the ferrules 41 in FIG. 10 are inserted into small diametered portions 45b at forward ends of the receiving trunks 45 in FIG. 11, and the large diametered portions 45a in the backward half of the receiving trunks 45 enter along inner wall faces of the engaging chambers 52 of the housing 26. On this occasion, distal ends of the small diametered portions 41a of the ferrules 41 come in contact with distal ends of the sleeves 14 to connect respective wave guide passages (not shown) in the centers of the ferrules 41 and the sleeves 14.
One of the light converting elements 12, that is, the light emitting element 12 converts an electric signal from the circuit board 39 to an optical signal and transmits it to one of the optical fiber cables 33 (See FIG. 9), while the other light converting element 12, that is, the light receiving element 12 converts an optical signal from the other optical fiber cable 33 to an electric signal and transmits it to the circuit board 39.
In an optical connector of a type in which the sleeves 14 are not provided (not shown), the ferrules 41 inserted into the receiving trunks 45 directly contact the light converting elements 12. In some other cases, the distal ends 41a of the ferrules 41 are exposed to the exterior from the housing 26.
However, in the conventional optical connector, it has been difficult to stably support the ferrules inside the housing of the male type optical connector 21 without a backlash. Moreover, there has been such an anxiety that because an outer shape of the housing 26 is rectangular as shown in FIG. 9, while an inner shape of the engaging chambers 52 is circular to conform to a shape of the receiving trunks 45, and so, local difference in wall thickness of the housing is large, the inner shape of the engaging chambers 52 tends to be deformed into an oval shape out of a perfect circle, due to molding sink or distortion at high temperature when molding synthetic resin.
In such cases, when the male and female type optical connectors 21 and 36 are engaged with each other, respective centers of the receiving trunks 45 and the engaging chambers 52 may become offset, resulting in offsets between respective centers of the sleeves 14 in the receiving trunks 45 and the ferrules 41 in the engaging chambers 52, or offsets between respective centers of the ferrules 41 and the light converting elements 12 (in case where the sleeves 14 are omitted). Thus, there occurs such an anxiety that reliable connections of the optical fiber cables 33 (optical connection) may not be conducted.
In view of the above described circumstances, an object of the invention is to provide an optical connector in which deformation of the engaging chambers in the male type optical connector is prevented, ensuring accurate centering of the ferrules in the engaging chambers, and at the same time, accuracy of the centering of the ferrules can be maintained favorably at any time, even though an outer force is exerted to the male type optical connector or a distorting force or so is applied during engagement of the male and female type optical connectors.
In order to attain the above described object, there is provided, according to a first aspect of the present invention, an optical connector comprising a housing, at least one annular wall provided in the housing and exposed to the exterior, a ferrule for an optical fiber cable being adapted to be inserted into the annular wall, and a protective frame wall provided around the housing so as to project higher than the annular wall.
According to a second aspect of the invention, the frame wall is so arranged as to surround the annular wall.
According to a third aspect of the invention, the frame wall is projected upwardly and downwardly from both top and bottom sides of the housing.
According to a fourth aspect of the invention, a wall for mounting a ferrule locking member is formed integrally with the annular wall, the wall being positioned at the same height as the frame wall and continued from the frame wall.
According to a fifth aspect of the invention, a pair of the annular walls are arranged in parallel in proximity to each other.
According to a sixth aspect of the invention, a receiving trunk in a mating housing continued to a light converting element is adapted to be inserted into the annular wall, and the ferrule is adapted to be inserted into the receiving trunk.
According to the first aspect of the invention, because the annular wall in the housing for receiving the ferrule for the optical fiber cable is protected by the frame wall, even when the annular wall is trampled by foot, or interferes with the exterior during transportation, etc., or a strong prying force is applied when the optical connectors are engaged, the frame wall will bear the outer force and prevent the annular wall from the interference with the exterior. Thus, the annular wall will be prevented from deformation, enabling accurate centering of the ferrule with respect to the mating connector to be always performed, and ensuring a favorable optical connection at any time.
Moreover, because rigidity of the housing will be enhanced owing to the presence of the frame wall, there will be no molding sink, distortion nor deformation of the annular wall, when the housing is molded from synthetic resin or even though the housing is left at high temperature, attaining the same effects as described above. Because the molding sink, distortion and deformation of the annular wall are avoided, wall thickness of the annular wall can be made constant with high accuracy, and the centering of the ferrule can be conducted accurately. Further, by employing the exposed annular wall, the housing can be made compact in a vertical direction.
According to the second and the third aspects of the invention, because the annular wall is completely surrounded by the frame wall, the annular wall can be more reliably protected, and deformation of the annular wall can be more reliably prevented.
According to the fourth aspect of the invention, because the wall for mounting the ferrule locking member constitutes a part of the frame wall, the annular wall can be protected from a stronger outer force than in a case where the frame wall only is provided.
According to the fifth aspect of the invention, because the pair of the annular walls are arranged in proximity to each other, rigidity and strength of the annular walls are increased, to promote protectivity of the frame wall with respect to the annular walls, and at the same time, the housing can be made compact in a lateral direction.
According to the sixth aspect of the invention, the receiving trunk in the mating housing can be smoothly introduced into the annular wall which is free from distortion and deformation, improving engaging ability between the connectors. At the same time, the ferrule can be smoothly introduced into the receiving trunk without misalignment, and reliability of the optical connection between the optical fiber cable and the light converting element can be improved.